Investigations On Damage And Fracture Of Gradient Particle Composites

The proposal of functionally graded materials(FGMs)designs has greatly fostered the development of composite materials.The method of continuously changing material composition or structure in some prescribed direction eliminates macro-level discontinuous interfaces,thus better material properties are usually obtained.Nowadays,FGMs have been widely used in various engineering and technological problems.Meanwhile,increasing studies have been conducted.However,existing research about the damage and fracture of FGMs has mainly focused on the metal-based ceramic particles FGMs,studies on the failure of brittle matrix FGMs are urgently required.This problem is investigated in the present study by using the improved generalized beam(GB)lattice model.Our work intentions provide some reference for the modeling and design of gradient particle composites,and can be summarized as the following three aspects:1.A GB model for simulating damage and fracture of gradient particle composites is established.A particle projection method has been developed to implement a gradient distribution of the particles.Two kinds of particle gradient distribution in the material – gradients in particle size and particle content,respectively – have been studied.Corresponding failure processes are simulated,and the failure characteristics are analyzed.The capability of the proposed GB lattice model to simulate the damage of gradient particle composites is verified.2.Based on the time-dependent stress redistribution mechanism,the “over-brittle” issue remaining in the existing lattice models is overcome.The traditional lattice model cannot predict the damage-induced softening behavior of quasi-brittle media.The presented method successfully reproduces strain rate sensitivity and damage-induced softening in quasi-brittle failures.Simulation results show that the model works well for gradient particle composites.3.The confinement shear effect between particle and matrix is investigated in gradient particle composites.The difference between elastic moduli of matrix-and reinforcementphases causes the composite to exhibit a confinement shear effect under external loads.In this paper,simulations based on GB lattice model show that the confinement shear effect in particle composites is related to the matrix-aggregate difference in terms of elastic modulus,external loading direction and average particle spacing.